The purpose of this project is to study the physical, chemical, and ultrastructural properties of calcium phosphate salts, and to clarify the kinetic and thermodynamic processes and the interactions with substances of biological interest that uniquely enable calcium phosphate salts to carry out their specialized role in vivo. The properties of calcium phosphate salts are being studied with a variety of ultrastructural and physical-chemical techniques such as spectroscopic methods, x-ray diffraction, surface area analyses, chromatographic and standard analytical chemistry procedures. Currently, the principal effort under this project is to study the physicochemical effects biologically important ions such as fluoride, carbonate, organic anions such as citrate, and magnesium have on the texture, i.e., size/shape, of apatite crystals grown in vitro under constant physiological-like solution conditions. The aim of this study is to distinguish the direct effect these solution substances have on the texture of biological apatites from that brought about by the metabolic and matrix changes these substances induce in vivo.